Reaction vessels of the type used for forming diamonds from graphite are generally known to the art. See, for example, the text entitled "Modern Very High Pressure Techniques", edited by R. H. Wentorf, Jr., PhD, General Electric Research Laboratory, published by Butterworths, London, and the next entitled "The Physics of High Pressure" by Bridgeman, to which reference will be made in this disclosure. Also, as background, U.S. Pat. No. 3,118,177, issued to B. C. Von Platen, on Jan. 21, 1964, describes an improved autoclave of the type in which chemical processes may be carried on under extremely high pressure.
Generally speaking, the known diamond-forming reaction vessels include a thick steel outer shell, a large quantity of insulating material adjacent to the inner walls of the outer shell, and a reaction space or chamber within the insulating material. The reaction chamber includes high temperature heating means (e.g. an electric heating element), and a space to position the graphite raw material which will be converted into diamond products by the simultaneous application of high pressure and high temperature. The specific means used to generate the necessary high temperature and high pressure which must be applied to the graphite are conventional and well-known to those skilled in the art.
In the known reaction vessels of the aforementioned type, the insulating material between the central reaction space and the outer steel shell is of significant importance. The heat required for the diamond forming reaction is sufficiently great as to damage the outer steel shell of the reaction vessel and possibly cause it to disintegrate in a relatively short period of time. Thus, the insulating material is necessary to prevent much of this heat from reaching the outer steel shell. Even with the insulating material, the heating means in known reaction vessels must not be turned on for any extended period of time to further avoid damage to the outer shell. In practice, the heating means is switched off usually every few minutes, or in some instances every few seconds. The quantity of insulating material used in the known apparatus is quite large in proportion to the area of the outer steel shell. Accordingly, the actual reaction space provided by the known vessels is quite small and there is usually only enough room to accomodate graphite raw material of the size of approximately one centimeter in diameter. Accordingly, the diamond resulting from the high heat and pressure applied to the graphite in the reaction chamber is quite small.
It is an object of the present invention to provide a reaction vessel of the type adapted to form diamonds from graphite that eliminates most of the insulating material required by the known vessels to thereby provide a significantly larger reaction space within the reaction vessel. Due to the flexibility of the reaction time allowed by the invention, diamonds of a size significantly larger than that resulting from the known reaction vessels can be produced when the graphite is subjected to a relatively long reaction (e.g., months). On the other hand, diamond powder can be produced from a relatively short reaction time (e.g., minutes or seconds).